Anyone trying to go easy on carbs or save money packing a brown bag for work knows lunch meat's lure: Deli meats are cheap, convenient, and pretty damn tasty on a cheese board or in a sandwich. They're also excellent sources of protein, B vitamins, and certain minerals.

But that's where the good news ends. Consuming even small amounts of processed meats increases the risk of colorectal cancer, the New York Times reports. One slice a day (15 grams) leads to a 4 percent increase; a more typical serving of 50 grams of processed meat a day increases your colorectal cancer risk by nearly 20 percent, a 2011 review of studies found. Studies have also found links between the consumption of processed meats and stomach cancer, and an increased risk of breast cancer among women who eat the most processed meats.

Part of the problem is the nitrites and nitrates used in meat processing. Nitrites and nitrates give processed meats their vibrant pink color and tang; they're also preservatives that keep botulism at bay. But scientists also suspect that nitrites and nitrates may be involved in the formation of cancer-causing compounds in the body.

"The average person goes to the store and sees claims like 'organic, 'natural,' or 'no added nitrates or nitrites,' and they assume those meats are safer, and they're not," Bonnie Liebman, director of nutrition at the Center for Science in the Public Interest, a food safety advocacy group, told the New York Times.

So what's a sandwich lover to do? In general, avoid, but if all else fails, choose wisely. Here are the three worst offenders at the deli counter.

Salami

What most deli meats have going for them — protein — salami is relatively light on. One ounce of salami only has about 5 grams, and those three skimpy slices clock in at 110 calories. It's a triple threat — high in fat, saturated fat, and sodium.

Bologna

At least, unlike salami, bologna is cholesterol-free? So there's that. But bologna, in addition to its wonky spelling, also contains a whopping 265 milligrams of sodium in each slice. Plus, that one slice will cost you 75 calories—almost double the calories of roast beef. It's also pretty low in protein, so it won't keep you feeling like a lean, mean word processing machine through the cubicle-bound afternoon.

Mortadella

Ah, mortadella. Bologna's more glamorous cousin. The secret to rich mortadella are those white flecks — they're cubes of pork fat. With about 9 grams of protein per serving, mortadella has more to offer than salami and bologna, but it's a worthy contender on the salt front. With 560 milligrams of sodium, you'll have eaten up 23% of the recommended daily intake with one serving of this Italian lunch meat.

The takeaway

If sandwiches and brown bag lunches are workday workhorses, rely on leftovers from the previous night's roast to round out a sandwich; stuff roast chicken, pork loin, and turkey between two slices of bread to get a twofer from one night of cooking.